Reforming is generally known to the petroleum industry as a process for the treatment of naphtha fractions of petroleum distillates to improve their octane rating by producing aromatic components from components present in naphtha feedstocks. Reforming is a complex process and involves a number of competing processes or reaction sequences. These include dehydrogenation of cyclohexanes to aromatics, dehydroisomerization of alkylcyclopentanes to aromatics, dehydrocyclization of an acyclic hydrocarbon to aromatics, and hydrocracking of paraffins to lighter gases boiling outside the gasoline range. In addition, the dealkylation of alkylbenzenes and the isomerization of paraffins may occur in reforming processes. Many of the reactions occurring during reforming are not desirable owing to their deleterious effect on the yield of commercially valuable products or upon the octane of the products. For example, hydrocracking reactions produce light paraffin gases, e.g., C.sub.1 -C.sub.4, and reduce the yield of products boiling in the gasoline range.
The interest in reforming catalysts and catalytic reforming processes is fueled by a desire to improve the production (yield) of the gasoline fraction while concurrently increasing its octane, while also having sufficient catalytic activity to minimize the use of excessive temperature conditions for the strongly endothermic dehydrocyclization process.
Several catalysts have been generally employed for catalytic reforming. Catalysts comprising platinum on chlorinated-alumina supports and Pt-X on alumina or chlorinated-alumina supports, where X is rhenium, iridium or tin, have been used for reforming naphthas. In addition, several disclosures have been made for processes employing alternative reforming catalysts. For example, several patents have disclosed the use of the zeolite mordenite in reforming catalysts, e.g., see U.S. Pat. Nos. 3,546,102; 3,679,575; 4,018,711 and 3,574,092. In addition, the use of ZSM-type zeolites in reforming catalysts and/or processes have been disclosed in U.S. Pat. Nos. 4,104,320; 4,417,083; 4,434,311 and 4,347,394. Further, the use of various forms of zeolite L is disclosed in U.S. Pat. Nos. 4,104,320, 4,447,316, 4,347,394 and 4,434,311. U.S. Pat. No. 4,417,083 discloses a process for the production of aromatic hydrocarbons in the presence of a two-bed process configuration employing a catalyst containing from 0.1 to 1.5% by weight of at least one metal selected from the group consisting of platinum, rhenium, iridium, tin and germanium, and containing sulfur in an atomic sulfur/metals ratio of from 0 to less than 1, supported on a crystalline, zeolitic aluminosilicate compensated by alkali metal cations, having a pore dimension larger than 6.5 Angstroms. The zeolite component is employed as a carrier. Among the zeolites that can be used are the Faujasites X and Y, the zeolite L, the zeolite omega and the zeolite ZSM-4.
Although several chemical reactions occur during reforming, principal desired reactions are the dehydrocyclization of paraffins and the dehydrogenation of naphthenes. The dehydrocyclization of a paraffin, containing six carbon atoms, is known to be relatively difficult, with the ease of paraffins dehydrocyclization generally increasing with the number of carbon atoms. Accordingly, an acidic reforming catalyst capable of forming aromatics from C.sub.6 paraffins would also be considered as effective in the conversion of paraffins containing seven or more carbon atoms. This conversion of acyclic hydrocarbons to cyclized and dehydrogenated aromatic products produces valuable aromatic products. The octane of the gasoline fraction increases as a result of the decrease in paraffins and as a result of the increase in the higher octane value aromatic products.
Although the prior art catalysts for dehydrocyclization have included the use of Group VIII metals with chlorinated-alumina and selected zeolite supports, the prior art has generally not disclosed the use of molecular sieves as components with chlorinated-alumina based catalysts and has not disclosed the use of certain novel zeolitic molecular sieves as components of dehydrocyclization catalysts containing noble metals and chlorinated-alumina.
The instant invention relates to novel reforming catalysts and processes employing the molecular sieve UPH-Y (disclosed in Belgian Pat. No. 874,373, issued Feb. 22, 1979) as a component in reforming catalysts containing noble metals and alumina and/or chlorinated-alumina carriers.